Java學習篇之--檢測主機是否在線Ping

Ping技術哪家強？

        最近想寫個程序，檢測一下遠程主機是否在線，因而在網上找到了不少前輩的方法，如今總結一下，分享給你們，但願可以拋磚引玉：

        方法一：利用java.net包中的類InetAddress中的getByAddress()方法：

函數原型：
public static InetAddress getByAddress(byte[] addr)
                                throws UnknownHostException

public boolean isReachable(int timeout)
                    throws IOException

註釋： Test whether that address is reachable.

       

源碼：
package com.ryze.ping.test;

import java.io.IOException;
import java.net.InetAddress;
import java.net.UnknownHostException;

public class PingTest {

	public static void main(String[] args) throws UnknownHostException, IOException {
		InetAddress inet;
		inet = InetAddress.getByAddress(new byte[] { 127, 0, 0, 1 });
		System.out.println("Sending Ping Request to " + inet);
		System.out.println(inet.isReachable(5000) ? "Host is reachable" : "Host is NOT reachable");

		inet = InetAddress.getByAddress(new byte[] { (byte) 220, (byte) 181, 112, (byte)244 });
		System.out.println("Sending Ping Request to " + inet);
		System.out.println(inet.isReachable(5000) ? "Host is reachable" : "Host is NOT reachable");
	}
}

運行結果：
Sending Ping Request to /127.0.0.1
Host is reachable
Sending Ping Request to /220.181.112.244
Host is NOT reachable

        方法二：利用java.net包中的類InetAddress中的getByName()方法：

函數原型：
public static InetAddress getByName(String host)
                             throws UnknownHostException

源碼：
package com.ryze.ping.test;

import java.io.IOException;
import java.net.InetAddress;
import java.net.UnknownHostException;

public class PingTest {

	public static void main(String[] args) throws UnknownHostException, IOException {
	    String ipAddress = "127.0.0.1";
	    InetAddress inet = InetAddress.getByName(ipAddress);

	    System.out.println("Sending Ping Request to " + ipAddress);
	    System.out.println(inet.isReachable(5000) ? "Host is reachable" : "Host is NOT reachable");

	    ipAddress = "220.181.112.244";
	    inet = InetAddress.getByName(ipAddress);

	    System.out.println("Sending Ping Request to " + ipAddress);
	    System.out.println(inet.isReachable(5000) ? "Host is reachable" : "Host is NOT reachable");
	}
}

運行結果：
Sending Ping Request to 127.0.0.1
Host is reachable
Sending Ping Request to 220.181.112.244
Host is NOT reachable

        方法三：利用java.lang包中的類Runtime中的getRuntime()方法：

函數原型：
public static Runtime getRuntime()

註釋： returns the runtime object associated with the current Java application.

函數原型：
public Process exec(String command)
             throws IOException

註釋： Executes the specified string command in a separate process.

函數原型：
public abstract int waitFor()
                     throws InterruptedException

註釋： the exit value of the subprocess represented by this  Process  object. By convention, the value  0  indicates normal termination.

源碼：
package com.ryze.ping.test;

public class PingTest {

	public static void main(String[] args) {
			    
	    boolean reachable = false;
	    Process process;
	    try {
	    	String ipAddress = "127.0.0.1";
			process = Runtime.getRuntime().exec("ping " + ipAddress);
			int returnVal = process.waitFor();
			reachable = returnVal == 0?true:false;
			System.out.println("Sending Ping Request to " + ipAddress);
			System.out.println(reachable ? "Host is reachable" : "Host is NOT reachable");
			
			ipAddress = "220.181.112.244";
			process = Runtime.getRuntime().exec("ping " + ipAddress);
			returnVal = process.waitFor();
			reachable = returnVal == 0?true:false;
			System.out.println("Sending Ping Request to " + ipAddress);
			System.out.println(reachable ? "Host is reachable" : "Host is NOT reachable");
		} catch (Exception ex) {
			ex.printStackTrace();
		}
	}
}

運行結果：
Sending Ping Request to 127.0.0.1
Host is reachable
Sending Ping Request to 220.181.112.244
Host is reachable

        小結：經過google搜索加上本身親自實驗，發現前兩種方法只能ping通局域網內的Ip，對於外網的ip通常ping不通，第三種方法個人理解是至關於在本地DOS環境下進行ping，能ping通外網，可是每ping一次效率很低。